#include "iostream"
#include "string"
using namespace std;
int main(void)
{
    int a[3][3] = {{1, 2, 3}, {4, 5, 6}, {7, 8, 9}};
    // constexpr size_t row = 3, col = 3;
    for (auto &rows : a) //除内层数组不用引用类型，其余都用
        for (auto cols : rows)
            cout << cols << " ";
    return 0;
}